The present invention relates generally to a powertrain for use in, e.g., a vehicle, and, more particularly, a powertrain with an arrangement for synchronizing speeds of an engine and an input shaft between the engine and a drive train.
Automated manual transmissions are desirable in many vehicular applications, particularly because of how they tend to simplify the driving operation while still offering the operator a substantial amount of control that may not be available in automatic transmissions. Heavy duty trucks with automated manual transmissions are not typically released by the original equipment manufacturer to vocations such as construction where a vehicle may be fielded in an environment that may cause the vehicle to lose speed rapidly while shifting gears. A vehicle with an automated transmission can lose speed during a shift because torque from the engine that drives the wheels must be interrupted to disengage one gear and to engage the next gear selected.
Automated manual transmissions are shifted by first breaking torque of the engine to the drive train by both reducing the fuel to the engine and opening the main disconnect or master clutch. Next the transmission moves the gear engagement clutch to the neutral position. The main disconnect clutch is briefly closed to synchronize transmission shaft speeds to shift the gear clutch to the desired transmission gear. The main disconnect clutch is then closed and the engine resumes providing torque to the drive train.
Excessive loss of road speed while shifting an automated manual transmission may cause the transmission to either connect a gear that is outside of the engine operating range (here meaning below idle or above an engine governed speed) or cause the transmission to recalculate the appropriate gear for operation and engage that gear. This recalculation and gear engagement increases the time that engine torque is not provided to the wheels. Connection to a gear outside the engine operating range or excessive interruption of application of engine torque to the drivetrain can result in engine stall, engine over speed, and/or stoppage of the vehicle. Rapid loss of speed during shifting can occur in conditions such as where there are level roads made of soft, sandy, snowy, or muddy soil, very steep paved or unimproved road grades, typically over ten percent in inclination, and during plowing snow. Accordingly, vehicles that are expected to be subjected to such conditions are typically not provided with automated manual transmissions.
It is desirable to provide a powertrain that can minimize the possibility of engine stalling or damage due to attempts to engage a clutch between an engine and an input shaft when the input shaft is rotated at a speed outside of the operating range of the engine. It is also desirable to facilitate the use of automated manual transmissions and manual transmissions in applications such as those for vocational vehicles that tend to be subject to substantial loss of speed during shifting operations.
According to an aspect of the present invention, a powertrain comprises a prime mover, a transmission, an input shaft adapted to transmit torque between the prime mover and the transmission, an output shaft adapted to transmit torque between the transmission and a driveline, and a master clutch between the prime mover and the input shaft, the clutch being movable between a disengaged position and an engaged position in which the clutch is not and is adapted to transmit torque between the prime mover and the input shaft, respectively. An electric motor is arranged for torque transmission with at least one of the input shaft and the output shaft, and a controller is provided for controlling the electric motor to rotate the input shaft at a rotational speed within an operating range of the prime mover when the clutch is moved from the disengaged to the engaged position.
According to another aspect of the present invention, a method for shifting gears in a transmission comprises disengaging a master clutch between a prime mover and an input shaft to the transmission, shifting gears in the transmission while the master clutch is disengaged, engaging the master clutch between the prime mover and the input shaft after shifting gears in the manual transmission, and controlling a rotational speed of the input shaft after shifting gears and prior to engaging the master clutch so that the rotational speed of the input shaft is within an operating range of the prime mover.